From Railway

Railway database services are reachable from outside Railway through a TCP proxy. Databasezy copies them from there into the matching engine.

Coming soon: phase 2

The guided Railway preset is in preview and becomes generally available in rollout phase 2. You can already migrate with a connection string or the zb CLI as shown below; the Railway-specific checks run when the host is recognised.

Railway migration at a glance, from the migration source catalogue

Status	Coming soon · phase 2
Target engines	PostgreSQL , MySQL , Valkey , MongoDB (Percona Server)
How we read it	Connection string
Continuous sync	Yes, for PostgreSQL and MySQL
Provider preset	railway

Before you start

• A Databasezy instance of the matching engine, or use --create with --engine.
• TCP Proxy enabled on the database service.

Find the connection string

Enable TCP Proxy on the database service (Settings, Networking, Public Networking) and copy the public URL variable: DATABASE_PUBLIC_URL, MYSQL_PUBLIC_URL, REDIS_PUBLIC_URL or MONGO_PUBLIC_URL.

Railway notes

• Use the public TCP proxy URL; private networking hostnames are not reachable from outside Railway.

The private *.railway.internal host resolves only inside Railway, so the preset blocks it (private_endpoint). It recognises *.proxy.rlwy.net hosts and adds sslmode=require for PostgreSQL.

Migrate

Portal

1. Open the target PostgreSQL instance (create one first if you need to) and choose the Migrate in tab.
2. Under Source, pick Connection string and paste the URL. The host is recognised as Railway; you can also pick it from the provider list.
3. Choose Copy and sync to keep the target current until cutover, or Copy for a one-off copy.
4. Run Preflight and work through the checklist. Blocking items must be fixed before the copy starts.
5. Start the copy and follow Copy and Verify. Mismatches are listed per table or collection.
6. When the sync lag is low, stop writes and choose Cut over. The Report step keeps the timings and verification results.

CLI

shell

# Dry run: print the preflight checklist and the plan, change nothing
zb migrate --from "postgresql://postgres:[email protected]:12345/railway" --to inst_abc --mode copy_and_sync --dry-run

# Start it (or use --create --size s1 instead of --to to create the target)
zb migrate --from "postgresql://postgres:[email protected]:12345/railway" --to inst_abc --mode copy_and_sync

zb migrate status mig_123
zb migrate cutover mig_123     # when status says ready_for_cutover

API

shell

curl -sS https://api.databasezy.com/v1/orgs/$ZB_ORG/instances/inst_abc/migrations \
  -H "Authorization: Bearer $ZB_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "source": {
    "kind": "connection_string",
    "url": "postgresql://postgres:[email protected]:12345/railway",
    "provider": "railway"
  },
  "mode": "copy_and_sync"
}'

# Follow progress, preflight report and verification
curl -sS https://api.databasezy.com/v1/orgs/$ZB_ORG/instances/inst_abc/migrations/mig_123 -H "Authorization: Bearer $ZB_API_KEY"

# Cut over once the status is ready_for_cutover
curl -sS -X POST https://api.databasezy.com/v1/orgs/$ZB_ORG/instances/inst_abc/migrations/mig_123/actions/cutover -H "Authorization: Bearer $ZB_API_KEY"

The same flow applies to Railway MySQL (--engine mysql) and Redis (--engine valkey). MongoDB services target the MongoDB engine, which is coming soon. For copy and sync, the source needs wal_level=logical and a role with REPLICATION; preflight checks both. After cutover, replace the Railway-injected variables in your service with the Databasezy connection string (Railway platform guide) and turn the TCP proxy off.

Verify

Verification compares what the engine exposes: row counts per table for SQL engines, document counts per collection for document engines, key counts for key-value engines. Mismatches are listed in zb migrate status <mig_id> and the Verify step. Run your application’s tests against the new instance before you switch traffic.

Continuous sync and cutover

With copy and sync, the target keeps receiving changes after the copy. When zb migrate status reports ready_for_cutover (two lag samples in a row under 5 seconds):

1. Stop writes to the source: maintenance mode, scale writers to zero, or revoke the application user.
2. Run zb migrate cutover <mig_id> (or Cut over in the portal). The agent drains the last changes, copies sequence values (PostgreSQL), verifies again and stops replication. If the target cannot catch up in time, the cutover is abandoned and sync keeps running; nothing changes on either side.
3. Point the application at the Databasezy connection string and resume writes. zb migrate status shows the measured downtime.

Schema changes are not replicated, so freeze migrations between the copy and cutover. Details: what happens at cutover.

Sync applies to PostgreSQL and MySQL targets only; other engines from this source are copy only.

Roll back

A migration never deletes anything on the source. Until you decommission it, rolling back means pointing the application back at the source.

• Before cutover: cancel with zb migrate cancel <mig_id>. The publication, replication slot or replication channel the migration created is removed.
• After cutover: writes made on Databasezy are not on the source. For PostgreSQL, start the migration with --reverse-sync so the old database keeps receiving them after cutover and stays a valid fallback. Without it, copy the new data back with a migration in the other direction before you switch.

Troubleshooting

Preflight blocks the host with private_endpoint

The URL uses *.railway.internal. Use the public URL variable from the TCP proxy.

Preflight cannot connect to the source

Check that the source accepts connections from the egress addresses preflight prints, that the host is the public one and that the password has not been rotated. zb migrate --dry-run shows the exact URL that will be used after any rewrites.

Preflight lists blocking items

Each item has a machine code and a fix. Nothing is written to the target until every blocking item is resolved; warnings do not block.

The restore stops on an extension

The source uses an extension Databasezy does not ship. Drop it on the source if it is unused, or exclude the objects that depend on it with --exclude.

Sync is blocked with pg.wal_level or pg.replica_identity

Logical replication needs wal_level=logical on the source and a primary key (or REPLICA IDENTITY FULL) on every published table. Preflight lists the tables.

Sync is blocked on binlog or GTID settings

Continuous sync needs binlog_format=ROW, gtid_mode=ON, enforce_gtid_consistency=ON and a user with REPLICATION SLAVE and REPLICATION CLIENT. Preflight names whichever is missing.

For anything else, zb migrate status <mig_id> shows the failing step and its message. How migrations work describes every step.